A cage of this type is described in U.S. Pat. No. 6,447,169 B2. Typical examples of materials which are used for the manufacture of cages of this type are polyamides which are reinforced with glass or with carbon fibers (for example, PA66/GF). In this case, the cage has two side rims which are connected to one another by webs. One of the side rims is arranged on one side of the cage above the pitch circle and another side rim is arranged below the pitch circle.
These retaining lugs are formed as a rule on one of the side rims or, as in the example under consideration according to U.S. Pat. No. 6,447,169 B2, on the webs and protrude in the radial direction out of the cage over the rim or over the side walls. The retaining lugs engage into a corresponding annular groove on one of the bearing rings of the inclined ball bearing. The cages are held, preassembled together with the balls and the corresponding bearing ring to form a structural unit, via the retaining lugs on the bearing ring. Retaining lugs of this type are also suitable for axial travel limitation of the cage in a bearing.
During assembly of the cage on/in the bearing ring, the retaining lugs are compressed or expanded elastically until the retaining lugs snap into a corresponding annular groove on the bearing ring. In the region, at which the highest bending moments are produced on the retaining lugs during this assembly, the retaining lugs have to be stable enough not to deform permanently or to break when being pushed onto the bearing ring. For this reason, the material cross section of the retaining lugs on cages according to the prior art increases with decreasing distance from the webs, as viewed from the free end of the retaining lugs. Retaining lugs which have relatively large cross sections with low dimensions are therefore inherently advantageous for the stability of the retaining lugs. The retaining lugs which are described in the prior art under consideration are therefore of comparatively small and compact configuration.
In contrast, large cross sections are disadvantageous during the assembly of the cages on/in the bearing ring, as the assembly forces for pushing them on, for example onto an inner ring, are high counter to the resistance during the expansion of the retaining lugs. Moreover, the retaining lugs are then not of sufficient elastic configuration and are easy to damage on account of the high assembly forces and despite the compact design.
The dimensions of the retaining lugs are subject to limits in the inclined ball bearing, as only a small amount of installation space is available between the bearing rings of the inclined ball bearing.
The molding tools for the manufacture of the cages are of relatively complicated configuration. The aim is to design the geometry of the retaining lugs as simple as possible. For this reason, for example the flanks (flank faces), which face in the circumferential direction, of each of the retaining lugs are oriented parallel to one another in cages according to the prior art, for reasons of manufacturing technology.
The cages are frequently picked up and moved by means of grippers during automated assembly of the cages. In the process, the retaining lugs are often auxiliary means, by which the cages are gripped using the grippers. Here, in turn, retaining lugs having a small action face with relatively small dimensions are disadvantageous for the grippers.
The above-mentioned requirements for the stability of the cages and their retaining lugs are contradicted by the requirement for low material usage during their manufacture. Material for the manufacture of the cage can be saved if the cage generally has small material cross sections and is therefore of thin-walled configuration. Moreover, the cross sections and, in particular, transitions, for example from the web to the rims, should be uniform for reasons of manufacturing technology.
The thin-walled configuration is subject to limitations as a result of the requirements for high operating strength of the cage. If the cross sections at rims or side walls are too small, it is to be feared that deformations of the retaining lugs are transmitted to the rims/side walls and the latter break or are deformed plastically. Furthermore, thin-walled plastic parts are extremely unstable after removal from the die and frequently lose their intended shape or geometry during subsequent cooling and during storage.
The above-mentioned and contradictory requirements make the optimum design of cages having retaining lugs difficult.